Custom made. Modders would post their creations on the shoryuken forums, but I would check reddit or discord now. Price depends on the creation. I bought modded ps2/ps3 sticks for $100, but the cost goes up if the modders make their own custom cases.
New to MvC2? Unless it is a low tier tourney you are gonna see 10, maybe 15 characters tops even with the 50+ character cast. The obvious top 5 (Sent, Storm, Mags, Cable, Ironman), the support crew (Commando, Psylocke, Cyclops). Maybe a few of the more OG players running Doom/Strider. That is pretty much what you can expect. There are maybe another 5 or so characters you may see (Spiral, Dhalsim, Cammy, Blackheart, War Machine) and most of them only if a select few people are attending.
I like watching mvc2 vids but I’m sick of the same characters fighting I’d rather watch kids play this or Storm Magnito Sentenal Cable captain Commando should be banned